Backups are there so that they can be restored. If your only drive is dedicated to writing, then you may never bother reading anything, and that's bad because y

Backups are there so that they can be restored. If your only drive is dedicated to writing, then you may never bother reading anything, and that's bad because you should verify your backups. Also, tape is slow. The MB/s is pretty nice on the latest tech, but a tape is pretty big, so if you have a lot of stuff it'll take a good while. Google says it takes 9.25 hours to write a full LTO8 12TB tape. Which means that if you have a sizable backup, in case of needing a full restore you might well spend a whole week reading tapes. And that's not accounting for that something might suddenly break, and the time where that becomes important is right when you need something restored urgently.